Could your painful joints be rheumatoid arthritis?

More than 50 million Americans have some form of arthritis. Most forms of arthritis cause pain and swelling in your joints, places where two bones meet such as your knee or elbow.

Usually arthritis affects older people, like my mother-in-law in her 70s whose pain got so bad she eventually had hip replacement surgery. Now she's active and pain-free. That's typically osteoarthritis, which breaks down the cartilage in your joints.

But there's another type -- rheumatoid arthritis or RA -- and it can affect people when they are much younger, including young adults, teenagers and even children.

In RA, instead of cartilage around joints being worn down and causing pain, your own immune system is causing swelling and pain. Your immune cells are attacking your own body.

That's why RA is considered an "autoimmune" condition. Right now, it's a lifelong condition once it develops.

For Beth Anne Demeter of Palatine, Illinois, it began when she was just 13 and growing up in Cleveland. She had trouble straightening her knees and her small hands swelled so much they looked like sausages. Kids teased her.